[The neuronal mechanisms of the escape reaction to stimulation of the statocyst receptors in the freshwater snail].

Tilts of the freshwater snail Planorbarius corneus, resulting in statocyst receptor stimulation, induced the defensive reaction including pulling down of the shell, shortening of the foot, inhibition of locomotion and feeding. The preparation of the central nervous system has demonstrated that many inter- and motoneurons from different ganglia were involved in this reaction. Usually the reaction was of "all or none" manner. The repeated reaction of the second tilt could be evoked not earlier than 10-20 s after the previous one. It is concluded that the defensive reaction to statocyst receptor stimulation is a "fixed act" determined by a special central mechanism (a central program). The reactions to stimulation of statocyst receptors and skin nerve are proved to be generated by the same mechanism.